A Manufacture Of New Type Hot Mandrels With Heat-resistant And Wear-resisting In Perforating Seamless Steel Tubes

It was the hot mandrels, alone with their quality and service life, that directly effect the output and quality in production of seamless steel tube on account of their acts as a key technology components. A new type of hot mandrels had been developed in the paper with Cr₃C₂ based ceramic to improve properties of the heat-resisting and the wear-resisting.Ceramic of Cr₃C₂ has the advantages of resistant on high-temperature oxidation, excellent wear-resisting and high bend strength. Cr₃C₂ powders, with correct crystal structure and fine grains, had been accepted by vacuum carbonization. Then ceramic powders based on Cr₃C₂/Ni had been worked out. A optimization sintering temperature was tested by quantitative analysis of DTA and X-ray diffraction.The new type hot mandrels, with the advantage of heat-resistant and wear-resisting, were made by two methods as follow. The first was to work out a whole hot mandrel made of ceramic based on Cr₃C₂/Ni. The second was to produce that of complex materials, which consists of steel H13 on whose surface was carried out respectively flame spraying, plasma spraying and flame plating and then the hot mandrels was sintered in vacuum. The properties had been tested by DTA, SEM, EDS and strength test.It was found that the matrix of the hot mandrels, treated by flame plating and vacuum sintering, was combined better with the coating than those treated by flame spraying and plasma spraying. The composition and the structure of both the matrix and the intermediate layer treated by flame plating had analyzed in detail.The manufacture of the whole hot mandrel had been unsuccessful because the compaction was long and thin which caused low pressed density. The problem remains to be solved in future.